This research will quantitatively evaluate the relationships among daily mortality, temperature, and air pollution in the U.S. during 1980-1989. The first phase will be devoted to the acquisition, access, aggregation, quality assurance, and descriptive analyses of the voluminous mortality, weather, and pollution data to be evaluated in this work. City-specific exploratory, frequency domain, and time series regression analyses will then be performed on a select subset of U.S. cities, followed by a more focused analysis of the 40 largest U.S. metropolitan areas. Finally, the results of these multiple city analyses will be integrated using meta- analysis methods in order to derive robust assessments of the respective influences of temperature and air pollution on U.S. mortality.This proposed research addresses several key research needs in the epidemiologic assessment of the human health consequences of these environmental factors: the high quality and comprehensiveness of the data to be employed in this research will greatly improve the generalizability of the results versus those of past studies; this analysis will apply advanced time series statistical procedures in order to appropriately address the autocorrelations and crosscorrelations present in such serial data; more biologically plausible specifications of temperature effects will be employed, and; this analysis, encompassing nearly half the U.S. population over 10 years, will provide the first large-scale time series assessment of the effects of ambient air pollution and temperature on U.S. mortality. As such, this research proposal represents an important effort to advance both the epidemiologic methods and scientific knowledge available for the assessment of the human health consequences of these environmental stresses. These advances are of critical importance, given our society's concerns about present-day pollution and about possible future health impacts of global warming.